1. Field of the Invention
The present invention relates to a fabrication system having a film formation system for depositing materials which can be deposited by vapor deposition (hereinafter, an evaporation material), a light emitting device which has a film containing an organic compound as a light emitting layer and for which the fabrication system is used, and a manufacturing method thereof. Specifically, the present invention relates to a film formation method (a vapor deposition method) for forming a film by vaporizing an evaporation material from a plurality of evaporation sources provided to be opposite to a substrate and a fabrication system.
2. Description of the Related Art
In recent years, research related to a light emitting apparatus having an EL device as a self-luminous light emitting device has been activated. The light emitting apparatus is referred to as an organic EL display or an organic light emitting diode. Since these light emitting apparatuses have characteristics such as rapid response speed that is suitable for a moving picture display, low voltage, low power consumption driving, they attracts an attention for next generation displays including new generation's mobile phones and portable information terminals (PDA).
An EL device has a layer containing an organic compound as a light emitting layer. The EL device has a structure in which a layer containing an organic compound (hereinafter, referred to as an EL layer) is sandwiched between an anode and a cathode. Electro luminescence is generated in the EL layer by applying an electronic field to the anode and the cathode. Luminescence obtained from the EL device includes luminescence generated in returning to a base state from singlet excited state (fluorescence) and luminescence generated in returning to a base state from triplet excited state (phosphorescence).
The EL layer has a laminated structure typified “a hole transporting layer, a light emitting layer and an electron transporting layer.” EL materials for forming an EL layer are classified broadly into low-molecular (monomer) materials and high-molecular (polymer) materials. The low-molecular materials are deposited using a vapor deposition system.
A conventional vapor deposition system has a substrate holder where a substrate is set, a crucible encapsulating an EL material, in other words, an evaporation material, a shutter to prevent the EL material to be sublimed from rising, and a heater for heating the EL material in a crucible. Then, the EL material heated by the heater is sublimed and deposited on a rolling substrate. At this time, in order to deposit uniformly, the distance between the substrate and the crucible needs to be 1 m or more.
According to a conventional vapor deposition system and a conventional vapor deposition method, when an EL layer is formed by vapor deposition, almost all the sublimated EL material is adhered to an inner wall, a shutter or an adherence preventive shield (a protective plate for preventing an evaporation material from adhering to an inner wall of a film formation chamber) at inside of the film formation chamber of the vapor deposition system. Therefore, in forming the EL layer, an efficiency of utilizing the expensive EL materials is extremely low i.e. about 1% or less and manufacturing cost of a light emitting apparatus becomes very high.
Further, according to a conventional vapor deposition system, in order to provide a uniform film, it is necessary to separate a substrate from an evaporation source at an interval equal to 1 m or more. Therefore, the vapor deposition system per se grows in size, a period required for exhausting each film formation chamber of the vapor deposition system is prolonged and therefore, film formation speed is slowed down and throughput is lowered. Also, in using a large area substrate, it may be a problem that the film thickness between a center portion and a marginal portion of a substrate is uneven. Further, the vapor deposition system has a structure for rotating a substrate and therefore, there is a limit in the vapor deposition system aiming at a large area substrate.
In view of the above-described problems, the present inventors have proposed a vapor deposition system (Reference 1. Japanese Patent Laid-Open No. 2001-247959 and Reference 2. Japanese Patent Laid-Open No. 2002-60926).